In a still camera, the importance of achieving accurate metering and registration of each image frame with the exposure gates in the frame-to-frame advance between exposures of a film strip has long been recognized Proper frame alignment with the picture-taking optical axis not only ensures correct frame-to-frame spacing and avoidance of overlap in a series of exposed images, but also correctly positions the film frame for properly locating exposure data and the like relating to a specific frame and recorded adjacent thereto on the film at the time of exposure for later reference in producing prints from the developed negatives. Harvey U.S. Pat. No. 4,639,111, for example, discloses marginal encoding by optical means adjacent a frame at the time of exposure of frame specific field of view identification information in a tele/pan camera.
Cameras incorporating an automatic wind-up drive mechanism for the frame-to-frame film transport between supply and take-up reels have means for stopping the advance of the film at a point of registration of the next available frame with a camera exposure station in alignment with the picture-taking optical axis. A common practice of achieving accuracy of metering and registration is to utilize film resident, frame correlated marginal fiducials, such as single or multiple perforations per frame, which can be detected to determine the correct positioning for the next frame. One system uses a single perforation per frame film and a mechanical claw or pawl that detects the perforation corresponding to the next frame and disengages the wind-up motor drive when that perforation reaches a desired stopping point (see, e.g., Beach U.S. Pat. No. 3,186,322). In another system (see, e.g., Takahashi U.S. Pat. No. 4,431,292), the film travel distance is tracked by counting the number of multiple perforations per frame which pass by a given point, such as over a toothed sprocket wheel in engagement therewith.
Once registration is achieved, it is desirable to provide means to maintain such registration until commencement of the next exposure. In the absence of such provision, the film is subject to creep out of registration due to vibration or physical shock forces exerted on the camera body or residual torque forces in the drive mechanism. For cameras designed to operate with a single perforation per frame film, registration can be maintained by continuing to engage the pawl at its stopping point through the perforation and into a slot located in the camera wall or film cartridge, until the next exposure. For sprocket wheel drives, the wheels can be locked to hold the frame in registration. It is a desirable objective to be able to achieve initial frame registration, as well as pre-exposure reassurance of continuation of registration, even for films that contain no marginal perforations at all and, thus, for which such pawl and sprocket drive systems are inadequate.
It is known to provide periodic film frame correlated fiducials or cues other than perforations for various post-exposure purposes. Yamada U.S. Pat. No. 3,622,235, for example, discloses a framing adjustment device which responds to a transparent optical locator signal spaced at periodic intervals along a marginal edge of a motion picture for automatically repositioning the picture during projection. In Staudacher U.S. Pat. No. 4,198,136 a motion picture film projector responds to interrupt-transport frame markings to signal a transition between those images which are to be sequentially displayed and those which are to be displayed as still images. Butler U.S. Pat. No. 4,215,920 shows marginal frame specific fiducials in the form of optically scannable binary representations of the sequential numerical identifications of successive frames. And, Williams U.S. Pat. No. 2,674,009 shows the use of marginal magnetic cue marks in the form of microscopicly thin metal disks which can be detected by magnetic scanning heads for the purpose of instituting an event or series of events (control or variation of printing light intensity, etc.) when a predetermined point or points are reached during the course of travel of a motion picture film.
The provision of a magnetic recording track on a still camera roll film for the purpose of storing various frame specific data relating to image exposure information (such as the photographing day, exposure conditions, photographing place, photographer, data for photographic laboratory use, and the like) is disclosed in Ohta U.S. Pat. No. 4,613,911. Ohta suggests the use of such a track as a recording medium for providing the camera with information regarding film sensitivity or the number of exposed or unexposed frames. There is, however, no disclosure or suggestion of using such a magnetic track for wind-up motor control to achieve initial frame registration, or for confirming and, if necessary, correcting a previously achieved alignment in preparation for a next exposure.